Welding electrode



Patented June 19, 1928.

UNITED STATES PATENT OFFIKCE,

ARTHUR STBOHKENGEB, OI IONDON, ENGLAND, ASSIGNDB TO THE QUASI-ABCOOIPANY- LIMITED, OF LONDON, ENGLAND.

WELDING ELECTRODE.

Io Drawing. Application filed June 17, 1928, Serial No. 116,730, and inGreat Britain September 18, 19.5.

This invention relates to electrodes such as are employed in the fusiondeposition of metals b the process known as arc welding an for cuttingor preparing metal I surfaces preparatory to welding or otheroperations.

For many years past it has been realized that in order to effectelectric welding with the deposition of fused metal the deposit shouldbe as free as possible from oxide or other impurities. It is of greatimportance to select a suitable covering material for the metallicelectrode which shall form a slag during the welding operation and willtend to remove impurities from the metal while also protecting the metalfrom ox1dation during deposition and cooling. Various forms of coveringmaterials have been proposed and used from time to time for' hispurpose, some of these being applied as a paste, while in recent yearsother forms of coverings have been developed, one which has ha a verylarge use being a covering of blue asbestosyarn or fibre wound spirallyaround the electrode. It has been recognized that blue asbestos containsa substan tial' proportion of iron in the form of ferrous silicate, andits favourable effects have been attributed to the reducing action whichiron in the ferrous state is capable of exertin in the slag. In order toincrease this e ect, aluminium on an equivalent material havin a highafiinity for oxygen has-been use generally wound in with the covering inthe 85 form of a wire, stri or plating on the metallic core of the eectrode, and'electrodes made in this manner, as described for example inthe specification of in United States Patent No. 1,144,390, have en verysuccessful in practlce.

I have found, in comparing the results obtained from electrodes coveredwith various mixtures of blue asbestos with white asbestos and othermaterials, that the higher the percentage of iron, that is to say thenearer the covering material is to being pure blue asbestos of high ironcontent, the more effective in neral is the slag covering in producing te results desired. These re sults, however, depend according to myresearchnot only upon the Ereducing action of the slag which melts withthe core of the electrodes during the welding, and covers the surface asthe welding progresses, but also upon thevarious other characteristicsof the slag material. For example, it is most important that the slagshould flow evenly and regularly over the surface of the inolten metalcovering it completely, and forming a layer of suflicient thickness toinsure that the rate of cooling of the metal deposited will befavourable to the ultimate structure of the weld junction between thedeposited metal and the body of the metallic article on which thedeposit is being effected. The fusion temperature of the coveringmaterial is also important, and the fusion temperatur e of blue asbestoshas been found to make it more suitable as a covering material forelectrodes than most other substances, while the possibility of applyingit spirally around the electrode as a yarn is a matter of very greatpractical importance because it insures the even and regular fusion ofthe covering as the electrode core melts.

The slag resulting from some covering materials does not fuse evenly asthe electrode core is melted, and the slag forms an indifferent orirregular covering on the surface of the deposited metal, with theresult that not only is oxidation liable to occur, but the metal coolsin such a way that the junction between the welding metal and themetallic structure to which it is applied is liable to have a coarsecrystalline formation which tends to produce serious weaknesses in thiszone. Welds made with blue asbestos as a covering material upon theelectrodes are strikingly superior to welds made with other kinds ofslags applied to the electrode, but the research has shown that there isroom for further improvement in this respect. Attempts to increase theamount of iron by incorporating as'olid ferrous, oxide in the coveringmaterial, have not proved successful, possibly because of the necessityof applying such material as a paste involving other constituents whichrender the added oxide of iron inefiective for the purpose in view.

I have now found that it is possible to attain the desired result withthe use of minerals other than crocidolite, but which occur ina longcrystallineor fibrous form and which contain a higher percentage ofiron. One of these minerals is a'variety of hornblende known asamositeF; Whereas crocidolite contains generally from 24 to 28% orthereabouts -of iron, amosite contains generally well over 30% or iron,and sometimes nearly 40%. It is essentially an iron silicatebut theproportion of ferrous to ferric oxide in its composition is liable tovary substantially. In experiments which I have made with this material,using it alone or in a mixture with blue asbestos as a covering forelectrodes I have discovered that it has substantial advantages over anyother covering material, not only in the directions mentioned alreadybut in otherrespects, as hereinafter set forth. The slag resulting fromthis material has a high iron content and itsco-efli'cient of expansionis substantially different from that of deposited metal, with the resultthat as the. metal cools, the slag covering tends to separate from thedeposit, and is easier to remove than the slag resulting from blueasbestos alone. The slag formed does-not tend to separate from thedeposited metal until this latter has cooled down to a point well belowthat at which there is risk of oxidation, probably about from 200 ,to150 (1, so that the surface of the metal deposited is not deleteriouslyaffected even if the slag flies off on its own account at or below thistemperature. The improvement in the crystal -structure at the weld jointwhen the covering material contains the higher iron content ismosthnarked, the

crystals as shown byflphotomicrographs of sections of the weld at theweld junction being comparatively small and very uniformly distributed.Iran only attribute this result to an improved annealing effect due tothe use of this new covering material.

Although amosite, when'used as the main constituent of the coveringmaterial, has all the advantages set forth, yet certain inci dentaldifficulties arise in connection with its use. Amosite fibres are "foundto be considerably more brittle than those of blue asbestos, so that the'material is more difficult to card and to spin into yarn. Further, whenamosite is used as the covering material, the slag is more viscous thanthat from blue asbestos, probably owing to its -7 high iron content, andthis renders the operation of welding with amosite-covered .electrodesrather more diflicult. The operator has ,to'be particularly careful toavoid trapping slag in the .weld metal. For these reasons I prefer touse a mixture of blue asbestos and'amositefibres, which can be cardedand spun together, the spun mixture being very suitable for use as anelectrode covering material. It has the requisite strength for winding,and the slag flows more freely so that welding is facllitated, and theresults are more uniform and reliable. I find that a mixture of aboutequal parts of blue asbestos and amosite is very suitable for allpurposes, as the yarn has the necessary strength, the addition of theamosite substantially increases the iron content in the slag, and thewelds havea high resistance to fracture, as tested by alternating impactand bending stresses, or in any other effective manner.

Although amosite ,has been referred to as the material preferably usedto increase the iron content of the electrode covering, it is to beunderstood that any mineral consisting essentially of silicate of ironcrystals in a long fibrous form, so that it can be spun into yarn orotherwise applied as a fibrous covering to the core of an electrode, maybe used provided that its percentage content of iron is sufficient forthe purpose in view. The improvements which I have noted are most markedwhen forms f amosite con- ,taining f om 35% of iron upwards are used,

but a s' bstantial improvement over anything obtainable with bli1easbestos and other covering materials aloneis noticeable even when theiron content of the covering material is but little more than 30%. v Thecovering material or mixture of materials is preferably spun into yarnand applied to the electrode core by winding spirally thereon with' theuse of sodium silicate or other material of a similar. character tosecure the turns of the yarn upon the electrode and to make a paste orcement which may be added to by impregnating the electrode with anyother materials in solution or suspension. Although it is preferable toapply the material as a yarn, the fibrous material may be lapped aroundthe electrode in any suitable manner, and the invention is not limitedto spinning the material into yarn before its ap licatlon.

he invention is also not limited to the" use of electr des covered withamosite alone or mixtures thereof with blue asbestos, for the-depositionof iron and ,steel, as the same covering material may be employed forelectrodes made of any of the metals which are capable of beingdeposited by fusion depo- I I claim as new and desire to secure by tersPatent is 1'. An electrode adapted for use in the weldin and cutting ofmetals, comprising a meta lic core with a covering of fibrous materialwrapped around it, said fibrous material consisting essentially of emixture on, said composite yarn consisting of a. mixof fibrouscrocidohte and amosite in the proture of fibrous crocidolite and amositeso portion of about one-halfQach. proportioned that the iron content isbe- 10 2. An electrode adapted for use in the ..tween 30 and 40 percent. 5 welding or cutting 0m metals comprising In witness whereof, Ihereto -subscribe my a metallic core with a covering in the form namethis 7th day of June,- A. D. 1926. of a composite yarn wrapped spirallythere- ARTHUR PERCY STBOHMENGER.

